They studied the sleeping patterns of 300 women aged between 17 and 26 and found that those who got less than 6.5 hours, or more than 8.5 hours, of sleep a night were more likely to be overweight.

They also found those who woke up at the same time each morning had lower body fat while those who stayed up late and slept in may be doing more harm than good when it comes to keeping the weight off.

Participants who had more than 90 minutes of variation in sleep and wake time during the week had higher body fat than those with less than 60 minutes of variation, researchers found.

According to them the secret was having between 8 and 8 1/2 hours sleep per night.

“We have these internal clocks and throwing them off and not allowing them to get into a pattern does have an impact on our physiology,” Professor Bailey said.

And while consistency in sleep patterns was important, BYU exercise science professor Bruce Bailey said the quality of sleep was also important, with people who slept well being more likely to keep the weight off.

Professor Bailey said sleep was often compromised as people tried to do too much in their day.

He said exercise, keeping a cool temperature in a cold, dark room and using beds only for sleeping would all help improve people’s sleep patterns.

“Sleep is often a casualty of trying to do more and be better and it is often sacrificed, especially by college students, who kind of wear it as a badge of honor,” he added.